A need exists for means to inject a nominally gaseous stream into a bed of slowly moving solid particles and to provide a reasonably uniform distribution of the gases across the bed diameter so that essentially all of the bed material in the horizontal plane of the injector can react with the gases. In general, this need arises for a moving bed chemical reactor in which the solids are in gravity flow. A specific example is in the field of coal gasification wherein small lump coal particles are fed onto a slowly downward moving particle bed into which it is desired to inject a mixture of hot reducing gases, steam, and/or a small amount of entrained solid particles. Such processes are normally carried out at severe conditions of temperature and pressure, for example, up to 2,000.degree. F. and 600 psi so that a rugged apparatus is required for this purpose. In addition to meeting these requirements, the injector must not significantly restrict the gravitational downward flow of solids in the reactor and should provide a capability for injecting gases, vapors, or liquids carrying entrained solids or pastes into the reactor bed. A capability for withdrawing of a nominally gas stream from within the particle bed is also a desired alternative.
Prior approaches such as injecting a gas stream from an unshielded perforated pipe or from gas ports around the periphery of the reactor have shown a tendency toward plugging of the ports of the pipe and/or a failure to provide the desired uniformity of gas distribution within the bed.